Carey, Frederick J

Introduction The superficial and deep parasternal intercostal plane (DPIP) blocks are two new blocks for thoracic pain. There are limited cadaveric studies evaluating the dye spread with these blocks. In this study, we examined the dye spread of an ultrasound-guided DPIP block in a human cadaveric model. Methods Five ultrasound-guided DPIP blocks were performed in four unembalmed human cadavers using an in-plane approach with a linear transducer oriented in a transverse plane adjacent to the sternum. Twenty milliliters of 0.1% methylene blue were injected between ribs 3 and 4 into the plane deep to the internal intercostal muscles and superficial to the transversus thoracis muscle layer. The chest muscles were dissected, and the extent of dye spread was documented in both cephalocaudal and mediolateral directions. Results The transversus thoracis muscle slips were stained in all cadavers from 4 to 6 levels. Intercostal nerves were dyed in all specimens. Four levels of intercostal nerves were dyed in each specimen with variability in number of levels stained above and below the level of the injection. Conclusions The DPIP block spreads along the tissue plane above the transversus thoracis muscles to multiple levels to dye the intercostal nerves in this cadaver study. This block may be of clinical value for analgesia in anterior thoracic surgical procedures.

Background and objectives Studies show variable spread with thoracic erector spinae plane (ESP) injections. Injection sites vary from lateral end of the transverse process (TP) to 3 cm from the spinous process, with many not describing the precise site of injection. This human cadaveric study examined dye spread of ultrasound-guided thoracic ESP block at two needle locations. Methods Ultrasound-guided ESP blocks were performed on unembalmed cadavers. Methylene blue (20 mL, 0.1%) was injected in the ESP at the medial TP at level T5 (medial transverse process injection (MED), n=7) and the lateral end of the TP between T4 and T5 (injection between transverse processes (BTWN), n=7). The back muscles were dissected, and the cephalocaudal and medial-lateral dye spread documented. Results Dye spread cephalocaudally from C4-T12 in the MED group and C5-T11 in the BTWN group, and laterally to the iliocostalis muscle in five MED injections and all BTWN injections. One MED injection reached serratus anterior. Dorsal rami were dyed in five MED and all BTWN injections. Dye spread to the dorsal root ganglion and dorsal root in most injections, though more extensively in the BTWN group. The ventral root was dyed in 4 MED and 6 BTWN injections. Epidural spread in BTWN injections ranged from 3 to 12 levels (median: 5 levels), with contralateral spread in two cases and intrathecal spread in five injections. Epidural spread in MED injections was less extensive (median (range): 1 (0–3) levels); two MED injections did not enter the epidural space. Conclusion An ESP injection administered between TPs exhibits more extensive spread than a medial TP injection in a human cadaveric model.